Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$167.98	13.506%	$190.6674	$190.67	$190.65	$190.70
Purchase #2	$222.31	13.296%	$251.8683	$251.87	$251.85	$251.90
Purchase #3	$146.88	3.837%	$152.5158	$152.52	$152.50	$152.50
Purchase #4	$159.42	7.842%	$171.9217	$171.92	$171.90	$171.90
Purchase #5	$50.46	8.399%	$54.6981	$54.70	$54.70	$54.70
Purchase #6	$91.71	9.113%	$100.0675	$100.07	$100.05	$100.10
Purchase #7	$107.76	13.409%	$122.2095	$122.21	$122.20	$122.20
7 purchase totals =	$946.52		$1,043.9483	$1,043.96	$1,043.85	$1,044.00